The state machine of the BQ2416x automatically changes primary states (Off, sleep, HiZ, charge disabled, charging, charge done, battery OVP, fault) based on data in the I²C registers, IN and USB pin voltages, BAT pin voltage and current flow, TS pin voltage, CD pin voltage and status of the safety timer. The BAT and TS pin voltages as well as current flow into the IN and USB pins, out of SYS pin and into/out of the BAT pin determine the charging sub-states, including conditioning, constant current (CC), CC with reduced charge current, constant voltage (CV) with reduced charge current.